This invention relates to a method and apparatus for separating and reclaiming lead oxide and metallic grid materials which compose plates such as are used in lead-acid storage batteries. As is well known, in the manufacture of battery plates, one type of lead oxide compound is pressed onto metallic grids for positive plates and another type of lead oxide compound is pressed onto grids for negative plates in a battery. Some of the grids inevitably come off of the pasting line with defects such as with pits in the paste or with corners which are not covered with paste. Since the plates have not been immersed in battery acid up to this time it is possible to remove the positive and negative oxide pastes from the grid and return the plates to the negative paste mixer for reuse in further production.
Manufacturers have used various methods for separating the paste from the grids. One method involves laying the defective grids out on a screen which is over a vat and then washing the paste off of the grids with a hose. Most of the water is then separated from the slurry formed in the vat and the residual paste is returned to the process. Another method involves putting the plates in a drum which is supplied with water and tumbling the plates for about an hour to knock off the paste. The mixture of oxide slurry and metallic grid material is then spilled onto a screen to sift the paste particles from the grid scrap.
Known methods for reclaiming the components of battery plates are detrimental to the comfort, safety and health of those who are required to perform the method. There is always water containing lead oxide particles in the working environment due to spilling and splashing that is incidental to the method. Lead compounds are known to be hazardous to health. Even though the workers wear waterproof clothing, lead compounds deposit on them and expose them to the danger of lead poisoning. An even greater health hazard results from lead oxide particles inevitably becoming airborne even though the environment and the materials are kept wet. The size of the lead oxide particles is believed to range between 0.1 microns and 0.5 microns with most particles being below 0.3 microns although some are even smaller than 0.1 microns. These small particles are readily entrained by gas and vapor molecules in the atmosphere. Inhalation of lead compounds is even more detrimental to health than skin contact. Some workers exhibit the symptoms of lead poisoning after a very short exposure to such environment.
Besides being detrimental to health, prior methods of reclaiming the paste and grids from the battery plates are uneconomical and especially unsuitable for use in a high production plant where even a small percentage of rejects results in a substantial volume of plates to be reclaimed.